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University of Pennsylvania 1st Partial Exam 1
University of Pennsylvania Final Exam
Department of EE

EE216

May 9, 2000
1.

Calculate the voltage V
S
that must be supplied to obtain 2kW, 240 0
o
Vrms, and a
power factor of 0.9 lagging at the load Z
L
in the network in Figure 1. (10pts)
Figure 1 Figure 2
2.

Find V
0
in the network in Figure 2. (10pts)
3.

Sketch the magnitude characteristic of the Bode plot for the transfer function. (10pts)
2
2
2
)
1
01
.
0
)(
1
1
.
0
(
)
1
(
)
(
1
.
0
)
(
+
+
+
=
jw
jw
jw
jw
jw
H
4.

Consider the network in Figure 3. If
R
=1k ,
L
=20mH,
C
=50
µ
F, determine the
resonant frequency o
, the quality factor
Q
, and the bandwidth
BW
of the network for
(1)

R
S
= (5pts)
(2)

R
S
=10k (5pts)
Figure 3 Figure 4
5.

Assuming the diodes in the circuits of Figure 4 are ideal, find the values of the
labeled voltage V and current I. (10pts)
1 0
o
A
j
1 V
S
V
L
30 j
5 +

Z
L
+ V
o
2 j
2 j
2 + -j
1 -j
2 1

R
S
R
L
C
10k +10V
5k
10V
V
I
0V 2
6.

Provide two designs of shunt regulators using zener diode, which is specified as
follows: a)
Vz
=6.8V and
rz
=5 for
Iz
=20mA; b)
rz
=750 at
Iz
=0.25mA (nearer the
knee). The supply voltage is nominally 9V and varies by
±
10%. Assume no load.
Find the value of R, the line regulation, and the corresponding variation in output
voltage V
0
for the following two designs.
(1) diode current is 20mA (5pts)
(2) diode current is 0.25mA (5pts)
7.

A
pnp
BJT is biased to operated at
I
C
=2.5mA. What is the associated value of
g
m
? If =50, what is the value of the small-signal resistance seen looking into the emitter
r
e,
into the base
r ? If the collector is connected to a 10k load, with a signal of 10mV
peak applied between base and emitter, what output signal voltage results? (10pts)
8.

For the common-emitter amplifier shown in Figure 5, let
Rs
=2.5k , =100.
(a)

Find the value of
R
E
to establish a dc emitter current of 1mA. (5pts)
(b)

Find
Rc
to establish a dc collector voltage of +5V. (5pts)
(c)

For
R
L
=5k and
r
o
=100k , draw the small-signal equivalent circuit (hybrid- model) of the amplifier and determine its overall voltage gain
v
o
/v
s
. (10pts)
Figure 5 Figure 6
9.

Consider the common-base amplifier of Figure 6 with a 10k load resistor connected
to the collector via a large capacitor. Let
Rc
=10k ,
Rs
=50 , and
Vcc
=10V. Find the
value of
I
such that the input resistance at emitter is 50 , and find the resulting
voltage gain
v
o
/v
s
. Assume =1 and T-model. (10pts)
+

R
S
R
C
R
E
R
L v
o
v
s v
s
+

Vcc
-
15V
+15V
R
S
Rc
v
o
I -V
EE
R
L